Bumping gaia.json for 2 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/7c8ef25c309b
Author: autolander <bug.autolander@gmail.com>
Desc: Bug 1108578 - merge pull request #26664 from KevinGrandon:bug_1108578_uninstallation_test_wait to mozilla-b2g:master

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https://hg.mozilla.org/integration/gaia-central/rev/fd6cc357517e
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1108578 - Try waiting for sendKeyButton to be displayed r=rudyl
Bumping manifests a=b2g-bump